Why do we use rats?

The laboratory rat has made invaluable contributions to cardiovascular medicine, neural regeneration, wound healing, diabetes, transplantation, behavioural studies and space motion sickness research. Rats have also been widely used to test drug efficacy and safety. Improved models in all these areas of research should result from our new knowledge of the rat genome.

Almost all disease-linked human genes have counterparts in the rat. Pinpointing these should help researchers to develop rat genetic models of human disease.

Rats are often used to study behaviour in psychology experiments. Their brains are larger than mice, and the animals are less timid and more intelligent. Although rats do not ‘think’ like humans, some of their brain structure resembles the more primitive elements of human brains, and hence they can be used to model some human behaviours.

Using rats, researchers showed that addiction manifests itself differently in different individuals and that, for some, compulsive cocaine-seeking behaviour continues despite adverse circumstances. Drug addiction had largely been regarded as the end point of a progressive loss of control over drug seeking resulting from a failure of part of the brain – the prefrontal cortex – that deals with decision making. However, our researchers were able to show that long term exposure to drugs also alters an area of the brain called the basolateral amygdala, which is associated with the link between a stimulus and an emotion.

In fact, using their rat model, our researchers have now identified a completely new path in the brain that links impulses with habits. This brain circuit links the basolateral amygdala indirectly with the dorsolateral striatum, which is the neural locus of habits.